Alex Ivanov

Selective crystallization of sulfate with a simple bis‐guanidinium ligand, self‐assembled in situ from terephthalaldehyde and aminoguanidinium chloride, was employed as an effective way to separate the highly hydrophilic sulfate anion from aqueous solutions. The resulting bis‐iminoguanidinium sulfate salt has exceptionally low aqueous solubility (K_sp=2.4×10⁻¹⁰), comparable to that of BaSO₄. Single‐crystal X‐ray diffraction analysis showed the sulfate anions are sequestered as [(SO₄)₂(H₂O)₄]⁴⁻ clusters within the crystals. Variable‐temperature solubility measurements indicated the sulfate crystallization is slightly endothermic (ΔH_cryst=3.7 kJ mol⁻¹), thus entropy driven. The real‐world utility of this crystallization‐based approach for sulfate separation was demonstrated by removing up to 99 % of sulfate from seawater in a single step.

Computational assessment of log K₁ values leads to novel design strategies for improving the ligand selectivity towards UO₂²⁺vs. VO²⁺/VO₂⁺.

We demonstrate a prediction of a novel hybrid material, a nanotube encapsulated 1D ionic LiP double-helix structure, suggesting that nanostructured confinement may be used to stabilize other zintl polyphosphide chains.

Binding strengths of salicylaldoxime–UO₂²⁺ complexes were quantified using UV/Vis spectroscopy and DFT.

A theoretical study of ozone isoelectronic Li₃N₃ species has been performed. Ab initio electronic structure calculations prove the viability of the ozone‐like Li₃N₃ molecule that might become synthesized. The predicted Li₃N₃ species with a novel N₃³⁻ molecular motif possess structural and chemical bonding features similar to that of O₃ molecules and can thus be considered as an “all‐nitrogen ozone”.

Aromaticity in porphyrins is described by the adaptive natural density partitioning analysis.

A theoretical study of Li₉₀P₉₀, which possesses a circular double‐helix structure that resembles the Watson–Crick DNA structure, is reported. This is a new bonding motif in inorganic chemistry. The calculations show that the molecule might become synthesized and that it could be a model for other inorganic species which possess a double‐helix structure.

IX (X=O, N, C) bonding was analyzed in the related hypervalent iodine compounds based on the adaptive natural density partitioning (AdNDP) approach. The results confirm the presence of a I→X σ dative bond, as opposed to the widely used IX notation. A clear formulation of the electronic structure of these hypervalent iodine compounds would be useful in establishing reaction mechanisms and electronic structures in bioinorganic problems of general applicability.

The structures and chemical bonding of TaBn− (n = 3–8) clusters are investigated systematically to elucidate the formation of the planar metal-centred aromatic borometallic cluster, Ta©B10− (the © sign is used to designate the central position of the doped atom in monocyclic structures in M©Bn-type planar clusters), which was found previously to have the highest coordination number for a metal atom in a planar geometry. Photoelectron spectroscopy is combined with ab initio calculations to determine the global minima of the TaBn− clusters. We find that from TaB3− to TaB5− the boron atoms nucleate around the central Ta atom to form fan-like structures. A structural transition occurs at TaB6−, which is found to have a hexagonal structure, but with a boron atom in the centre and the Ta atom on the periphery. TaB7− is shown to have a three-dimensional boat-like structure, which can be viewed as a Ta atom coordinated to an elongated B7 cluster from above. The global minimum of the TaB8− cluster is found to be pyramidal with the Ta atom interacting with a B8 monocyclic ring. Starting from this structure, additional boron atoms simply enlarge the boron ring to form the slightly pyramidal TaB9− cluster and eventually the perfectly planar Ta-centred B10-ring aromatic cluster, Ta©B10−. It is shown that boron atoms do not nucleate smoothly around a Ta atom on the way to the decacoordinated Ta©B10− molecular wheel, but rather the competition between B–B interactions and Ta–B interactions determines the most stable structures of the smaller TaBn− (n = 3–8) clusters.